1. Field of Invention
The present invention relates to temperature characteristic compensation apparatuses that compensate for the temperature characteristics unique to individual electric/electronic applied devices in various types.
2. Description of Related Art
An electronic device may be composed of a combination of thermo-sensitive resistances that have temperature characteristics, thermo-sensitive elements, such as conductors and semiconductor elements, and other components. In the past, when the temperature characteristic of the thermo-sensitive element is positively applied to the device, or when the temperature characteristic needs to be corrected due to its adverse effect, it was a general practice to compensate for the temperature characteristic unique to the thermo-sensitive element, and use it in the electronic device, or to provide as a countermeasure a thermo-sensitive element that has an offsetting temperature characteristic.
For example, thermistors are known as thermo-sensitive resistances that change their resistances depending on temperatures. There are thermistors that change the resistance in a positive correlation in which the resistance increases as the temperature elevates, and thermistors that change the resistance in a reverse correlation in which the resistance lowers as the temperature elevates. An electronic circuit may be designed through placing thermistors at key portions in the circuit to offset harmful effects by the temperature characteristics. More specifically, a majority of the conductors increases their resistance as the temperature elevates, but in reverse, some of the semiconductor elements may increase their conductivity. Their temperature characteristics may often be characterized by changes in curves of multiple degrees, exponential function, or logarithm, rather than in linear. If an electronic apparatus that is composed of such conductive and semiconductor elements has a harmful temperature characteristic, a correction to remove such harmful effect is made through offsetting the harmful effect.
FIG. 4 shows a circuit diagram of a reference voltage supply circuit 200 that uses a conventional band-gap voltage source, which is supplied with a first power supply (hereafter referred to as a “power supply VDD” or “VDD”) and a second power supply (hereafter referred to as a “power supply VSS” or “VSS”), and is composed of a constant voltage source 50 including a band-gap circuit 40, and a voltage follower circuit 60 that outputs a reference voltage VST that is generated by the band-gap circuit 40 through a terminal VREF with a low impedance at a constant voltage. The band-gap circuit 40 includes an N channel MOS transistor (hereafter abbreviated as a “N•transistor”) 53 and a N•transistor 54 connected to constant current paths 41 and 42, respectively, and the constant voltage source 50 is composed of a multiple-stage current mirror circuit having a plurality of constant current paths 41, 42, 43 and 44 including the band-gap circuit 40.
In FIG. 4, only the N•transistor 53 is of a depletion type, and other MOS transistors are all of an enhancement type.
The constant current path 44 that defines a last stage of the constant voltage source 50 includes a P•transistor 51 and an enhancement type P+ gate N-channel transistor (hereafter abbreviated as a “PGN-transistor”) 56 which are serially connected in this order from the VDD side, wherein the PGN•transistor 56 defines an output terminal V6 of the constant voltage source 50. An operation amplifier 61 having a minus input terminal that connects to the output terminal V6, and a P-transistor 62 having a gate G that connects to an output terminal J of the operation amplifier 61 compose the voltage follower circuit 60. A source S and a drain D of the P-transistor 62 and a load resistance (which may be hereafter abbreviated as “R4”) are serially connected from the VDD side in this order to the VSS. A connection point between the drain of the transistor 62 and the resistance R4 defines a terminal REF. The reference voltage VST is outputted from the VREF at a low impedance.
More specifically, when the reference voltage supply circuit 200 is connected to the power supplies VDD and VSS, a constant current starts to flow from the N•transistor 53, the current mirror circuit composed of the transistors P•transistor 58 and P•transistor 59 flows a current that is determined by the N•transistor 53, the N•transistor 55 is driven, the current mirror circuit composed of the P•transistor 50 and P•transistor 51 drives the PGN•transistor 56, a difference in Fermi level of the N•transistor 5 and PGN•transistor 56 is outputted from the terminal V6 as a reference voltage VST=1.05V, the operation amplifier 61 drives the P•transistor 62 to start flowing a current through the resistance R4, and a reference voltage VST that is the same as that on the terminal V6 is outputted from the terminal VREF due to the characteristic of the operation amplifier 61 with a high input impedance and a low output impedance.